A survey of virtual LAN usage in campus networks

VLANs are widely used in today's enterprise networks to improve Ethernet scalability and support network policies. However, manuals and textbooks offer very little information about how VLANs are actually used in practice. Through discussions with network administrators and analysis of configuration data, we describe how three university campuses and one academic department use VLANs to achieve a variety of goals. We argue that VLANs are ill-suited to some of these goals (e.g., VLANs are often used to realize access control policies, but constrain the types of policies that can be expressed). Furthermore, the use of VLANs leads to significant complexity in the configuration of network devices.